Temperature-responsive mixing valve

ABSTRACT

A temperature-actuated mixing valve for controlling outlet temperature in a fluid flow system including a valve housing having first and second inlets for introducing first and second respective supply fluids and an outlet. A shuttle assembly is positioned in the housing. A valve member is mounted within the housing and responds to the temperature of the supply fluids to vary their mixture ratio to dispense fluid at an outflow temperature. A shuttle member is positioned within the valve member, is moveable responsive to supply fluid temperature variation, and includes an elongate grip pad for manual removal of the shuttle member from the housing. A thermal actuator converts thermal energy into mechanical movement using a piston. A spring maintains the valve and shuttle members in a stationary condition relative to each other and permits movement of the shuttle member relative to the valve member for accommodating movement of the piston when the valve member has reached its limit of travel.

This application is a continuation of U.S. application Ser. No.09/516,125, which was filed on Mar. 1, 2000.

TECHNICAL FIELD AND BACKGROUND OF THE INVENTION

This invention relates to a temperature-actuated mixing valve of thegeneral type used to control in-line water temperature in potable hotwater systems. Such valves are typically used at the hot water source,such as at a gas or electric hot water heater or boiler. The temperatureof the water allowed to flow downstream from the mixing valve ismaintained within a predetermined range of temperature by mixing hot andcold water entering the valve on the upstream end. The invention istherefore described with reference to such a hot water system. However,principles of the invention also have application with other liquids andwith gases, and for this reason the application is intended to encompassboth liquids and gases, and liquids other than water.

Most prior art mixing valves utilize a thermal actuator, which acts asthe “motor” of the valve. Such actuators convert thermal energy intomechanical movement. The operating principle of most such devices isbased upon the large increase in volume of a thermosensitive materialsuch as wax which, when heated, changes from a solid to a liquid. Whensuch a thermosensitive material is enclosed within a confined space,heating causes the material to expand against a piston to perform work.In some cases such actuators are either provided with twooppositely-acting pistons to increase the range of motion, or two suchactuators are placed end-to-end to accomplish the same function. Byincorporating a thermal actuator into a mixing valve, hot and coldsupply pressures and temperatures can be regulated.

A common problem in the use of such devices is that if the shuttle hasmoved as far as it can move within the valve, but the piston of thethermal actuator is still trying to move, there must be some means ofconsuming this extra travel. Otherwise the valve can be damaged ordestroyed. This is most often accomplished in the prior art by the useof an overtravel spring mounted around an adjusting bolt in the top ofthe valve. This solution creates several additional problems. First,this arrangement adds height to the mixing valve, which may prevent orrestrict use in confined areas, or promote breakage under impact.Second, the overtravel spring must be preloaded, requiring a means forretaining the spring on the adjusting bolt. Finally, in applicationswhere two thermal actuators are used back-to-back, there must be someway to retain both elements in the shuttle.

In addition, mixing valves are often difficult to disassemble for repairor maintenance, and require the use of tools, often in confined spaces.

The design features of the present invention solve the known prior artproblems simply and efficiently.

SUMMARY OF THE INVENTION

Therefore, it is an object of the invention to provide a mixing valvewhich is compact.

It is another object of the invention to provide a mixing valve which iseasy to disassemble.

It is another object of the invention to provide a mixing valve in whichthe overtravel spring is integral with the shuttle assembly.

It is another object of the invention to provide a mixing valve in whichthe shuttle ccages the thermal element or elements, which permittingunrestricted movement within the full range of movement.

It is another object of the invention to provide a mixing valve whereinthe overtravel spring is remote from and operates independently of theadjustment bolt.

These and other objects of the present invention are achieved in thepreferred embodiments disclosed below by providing atemperature-actuated mixing valve for controlling outlet temperature ina fluid flow system including a valve housing having first and secondfluid supply inlets for introducing first and second respective supplyfluids and a fluid outlet for dispensing a fluid at a predeterminedoutflow temperature. The mixing valve includes a shuttle assemblypositioned in the housing. The shuttle assembly comprises a valve membermounted for movement within the housing responsive to the temperature ofthe supply fluids to vary the mixture ratio of the first and secondsupply fluids as required to dispense fluid at the predetermined outflowtemperature. A shuttle member is positioned within the valve member andis moveable as a unit therewith within a predetermined range of motionresponsive to supply fluid temperature variation. The shuttle memberincludes an elongate grip pad for permitting the shuttle member to bemanually removed from the valve housing without the need for tools. Athermal actuator is provided of the type which converts thermal energyinto mechanical movement by movement of a piston. A first end of thethermal element engages the movable shuttle member and an opposingsecond end engages a stationary portion of the housing whereby movementof the piston of the thermal actuator produces corresponding movement ofthe valve member. An overtravel spring is captured in a compressedcondition between the valve member and the shuttle member formaintaining the shuttle member and the valve member in a stationarycondition relative to each other within the predetermined range ofmotion of the valve member and for permitting movement of the shuttlemember relative to the valve member sufficient to accommodate movementof the piston of the thermal actuator when the valve member has reachedits limit of travel without accommodating the full extent of movement ofthe piston of the thermal actuator.

According to one preferred embodiment of the invention, the valve memberis generally cylindrical and includes sealing means for sealing thevalve member against fluid flow between the valve member and adjacentcylindrical walls of the valve housing.

According to another preferred embodiment of the invention, the shuttlemember includes retaining means for retaining the thermal actuatorwithin the shuttle member while permitting movement of the pistonresponsive to the temperature of the inlet fluids.

According to yet another preferred embodiment of the invention, theretaining means comprises a plurality of elongate fingers axiallyaligned with the longitudinal axis of the thermal actuator, each of thefingers having a radially inwardly-extending detent for interfering withmovement of the thermal actuator beyond a predetermined range of motionfor movably-capturing the thermal actuator within the shuttle member.

According to yet another preferred embodiment of the invention, the grippad extends along the longitudinal axis of the shuttle member.

According to yet another preferred embodiment of the invention, thevalve member includes an annular shoulder defining a support for theovertravel spring. The valve member includes locking means for receivingand locking the shuttle member within the valve member. The lockingmeans cooperates with the overtravel spring for maintaining the shuttlemember and the valve member in the stationary condition relative to eachother.

According to yet another preferred embodiment of the invention, thelocking means comprises a plurality of locking channels formed withinthe area of the valve member accommodated by the overtravel spring, eachof the locking channels having a first segment communicating with aninwardly-facing end of the valve member, a second segment communicatingwith the first segment and extending peripherally around inner wall ofthe valve member and a third segment spaced apart from the firstsegment, communicating with the second segment and terminating at ablind end within the inner walls of the valve member, the plurality oflocking channels adapted to receive respective ones of a plurality oflocking tabs carried by the shuttle member and lock the shuttle memberin the valve member by compressing the overtravel spring and passing theplurality of locking tabs through the first and second segments and tothe blind end of the third segment of the locking channels.

According to yet another preferred embodiment of the invention, theshuttle member comprises an elongate stem having an annular bore forreceiving the thermal actuator therein for movement therein, retainingmeans for retaining the thermal actuator in the bore and locking meansfor locking the stem in the valve member.

According to yet another preferred embodiment of the invention, thevalve housing includes an adjusting bolt engaging an end of the thermalactuator remote from the valve member for permitting longitudinaladjustment of the thermal actuator relative to the valve member.

According to yet another preferred embodiment of the invention, thethermal actuator comprises a pair of thermal actuators for increasingthe effective range of temperature-responsive motion.

According to yet another preferred embodiment of the invention, theretaining means comprises a cage within which the thermal actuator iscaptured.

An embodiment of the method according to the invention controls outlettemperature in a fluid flow system including a valve housing havingfirst and second fluid supply inlets for introducing first and secondrespective supply fluids and a fluid outlet for dispensing a fluid at apredetermined outflow temperature, the mixing valve including a shuttleassembly positioned in the housing. The method comprises the steps ofmounting a valve member for movement within the housing responsive tothe temperature of the supply fluids to vary the mixture ratio of thefirst and second supply fluids as required to dispense fluid at thepredetermined outflow temperature. A shuttle member is positioned withinthe valve member as a unit with the valve member within a predeterminedrange of motion responsive to supply fluid temperature variation. Theshuttle member includes an elongate grip pad for permitting the shuttlemember to be manually removed from the valove housing without the needfor tools. A thermal actuator is provided of the type which convertsthermal energy into mechanical energy by movement of a piston wherein afirst end of the thermal element engages the movable shuttle member andan opposing second end engages a stationary portion of the housingwhereby movement of the piston of the thermal actuator producescorresponding movement of the valve member. The shuttle member and thevalve member are maintained in a stationary condition relative to eachother within the predetermined range of motion of the valve member whilepermitting movement of the shuttle member relative to the valve membersufficient to accommodate movement of the piston of the thermal actuatorwhen the valve member has reached its limit of travel withoutaccommodating the full extent of movement of the piston of the thermalactuator.

Another embodiment of the method according to the invention comprisesthe step of retaining the thermal actuator within a cage forming a partof the shuttle member for permitting movement of the thermal actuatorwithin its range of motion while preventing the thermal actuator fromfalling out of the shuttle assembly.

According to another preferred embodiment of the invention, a method isdisclosed for controlling outlet temperature in a mixing valve of afluid flow system includes a valve housing having first and second fluidsupply inlets for introducing first and second respective supply fluidsand a fluid outlet for dispensing a fluid at a predetermined outflowtemperature, the mixing valve including a shuttle assembly positioned inthe housing and carrying a thermal actuator responsive to thetemperature of fluid entering the mixing valve for controlling the ratioof the respective supply fluids to regulate the outflow temperature ofthe fluid. The method comprises the step of forming the shuttle assemblyfrom a shuttle member and a valve member releasably-attached together.The shuttle member includes an elongate grip pad for permitting theshuttle member to be manually removed from the valve housing without theneed for tools. The method further includes the steps of retaining anovertravel spring between the shuttle member and the valve member,moving the shuttle member and the valve member as a unit responsive tothe thermal actuator when regulating the flow of fluid flowing into themixing valve, and moving the shuttle member relative to the valve memberwhen compensating for overtravel of the thermal actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the objects of the invention have been set forth above. Otherobjects and advantages of the invention will appear as the inventionproceeds when taken in conjunction with the following drawings, inwhich:

FIG. 1 is a vertical cross-section of a typical prior arttemperature-responsive mixing valve;

FIG. 2 is a top view of a temperature-responsive mixing valve accordingto a preferred embodiment of the invention;

FIG. 3 is a vertical cross-section taken substantially along line 3—3 ofFIG. 2;

FIG. 4 is a fragmentary perspective view of the shuttle assembly portionof the mixing valve shown in FIGS. 2 and 3;

FIG. 5 is a fragmentary perspective view according of the shuffleassembly with the overtravel spring removed to more clearly shown themanner of locking the shuttle member into the valve member;

FIG. 6 is a top plan view of the shuttle assembly portion of the mixingvalve shown in FIG. 3;

FIG. 7 is a vertical cross-sectional view taken substantially alonglines 7—7 of FIG. 6;

FIG. 8 is an exploded perspective view of the shuttle assembly portionof the mixing valve shown in FIG. 3;

FIG. 9 is an exploded view of a temperature-responsive mixing valveincluding a shuttle assembly according to one embodiment of theinvention; and

FIGS. 10-13 are vertical cross-sections of the mixing valve generally asshown in FIG. 9 in various temperature-responsive flow positions.

DESCRIPTION OF THE PREFERRED EMBODIMENT AND BEST MODE

Referring now specifically to the drawings, a prior arttemperature-responsive mixing valve 10 is shown. Note generally that theprior art shuttle assembly 11 is moved by a thermal actuator 12 which ismaintained in a tensioned condition by a spring 13, which returns thethermal actuator 12 to its initial position. Another spring 16 capturedon the other side of the thermal actuator 12 by an adjustment bolt 17provides overtravel protection to the shuttle assembly 11. Thisarrangement results in a valve housing which is relatively large, as isevident from the overall length taken up by the shuttle assembly, spring13 and spring 16. The shuttle assembly 11 is rigidly attached via athreaded connection to the thermal actuator 12.

As is shown in FIGS. 2-13, the mixing valve 20 according to a preferredembodiment of the invention is simple, compact, efficient and easy toassemble and disassemble. As is generally shown in FIGS. 2 and 3, mixingvalve 20 includes a cast housing 21 which includes a hot water supplyinlet 22, and cold supply water inlet 23 and an outlet 24 fordischarging a mixture of the hot and cold water downstream. A removablethreaded plug 25 positioned in a threaded bore 26 in the housing 21permits access to the internal parts of the mixing valve 20, asdescribed below.

As is generally shown in FIG. 3, a shuttle assembly 30 is positionedwithin the mixing valve 20 and regulates the temperature of waterflowing from the outlet 24. Shuttle assembly 30 includes an annular,hollow valve member 40 which is releasably locked to a shuttle member50. The shuttle member 50 carries a pair of thermal actuators 70A, 70Bwhich move the valve member 40 responsive to the temperature of thewater flowing into the housing 21 through the inlets 22 and 23. Thethermal actuators 70A, 70B are rigidly coupled together, with, forexample, a brass collar 71. An adjustment screw 80 is threaded into thetop of the housing 21 and is seated against an adjustment plug 81 whichalso engages the top end of the thermal actuator 70A. The adjustmentscrew 80 is used to calibrate the adjustment of the valve member 40. Aspring 82 is seated in the plug 25 and urges the shuttle member 50 andthe thermal actuators 70A, 70B upwardly into engagement with theadjustment plug 81.

An overtravel spring 85 is positioned within the hollow bore of thevalve member 40 and cooperates with the shuttle member 50 to accommodatemovement of the thermal actuators 70A, 70B beyond the range of thetravel of the valve member 40 within housing 21. Further explanation ofthe operation of the mixing valve 20 follows a more specific descriptionof the shuttle assembly 30.

While the shuttle member 50 and valve member 40 can be fabricated frommany suitable materials, which must be moldable or machinable, anddimensionally stable over a wide range of temperatures, one suitablematerial is a glass-filled plastic such as modified polyphenylene ether(“PTE”) such as sold under the trademark “Noryl.”

Referring now to FIGS. 4 and 5, the shuttle assembly 30 is shown in twodifferent views with (FIG. 4) and without (FIG. 5) the thermal actuators70A, 70B and overtravel spring 85 in place. Valve member 40 includes aninterior shoulder 41 on which one end of the overtravel spring 85 rests.An annular groove 42 on the outer surface accommodates an O-ring 43which seals the valve member 40 against the interior walls of thehousing 21. (See FIG. 3). Valve member 40 also includes fourthree-segment locking channels 44A-D on the interior walls. Each lockingchannel 44A-D communicates with the top end of the valve member 40 andis adapted to receive one of four integrally-formed locking tabs 51A-D.Each locking channel 44A-D is generally U-shaped and extends along thelongitudinal axis of the interior wall of the valve member 40, laterallyacross the inner periphery of the inner wall of the valve member andthen along the longitudinal axis of the interior wall of the valvemember 40 to a blind end.

The shuttle member 50 is locked into the valve member 40 by insertingone of the locking tabs 51A-D into a respective one of the lockingchannels 44A-D. Significant force must be applied to force the lockingtabs 51A-D into the locking channels 44A-D against the force of theovertravel spring 85. When the locking tabs 51A-D reach the level of thelaterally-extending segment of the locking channels 44A-D the shuttlemember 50 is twisted relative to the valve member 40, moving the lockingtabs 51A-D along the periphery of the valve member 40 to the respectiveblind ends of the channels 44A-D. The tension of the overtravel spring85 securely locks the shuttle member 50 in the valve member 40 whilestill allowing longitudinal movement of the shuttle member 50 relativeto the valve member 40 when necessary to accommodate overtravel of thethermal actuators 70A, 70B. Within the normal range of movement of thevalve member 40, the shuttle member 50 and the valve member 40 movetogether in fixed relation to each other.

Shuttle member 50 also includes four fingers 54A-D which extend alongthe longitudinal axis of the shuttle member 50 and surround a recess 55within the thermal actuators 70A, 70B are positioned. Each of thefingers 54A-D have radially inwardly-directed detents 56 which engageand interfere with an enlarged annular ring 72 on the innermost thermalactuator 70B. This prevents the thermal actuator 70B from falling fromthe shuttle member 50. Rather, a pulling force must be applied to thethermal actuator 70B sufficient to cause the ring 72 to outwardly deformthe fingers 54A-D sufficiently to permit the thermal actuator 70B to beremoved. In instances where only a single thermal actuator 70B is used,it is captured and held in exactly the same manner.

Finally, the shuttle member 50 also includes an integrally-formed fingergrip pad 76 which permits the shuttle member 50 and other attachedcomponents to be removed merely by inserting the hand into the housing21 through the threaded bore 26 after removal of the plug 25. The entireassembly can then be removed from the housing 21.

FIGS. 6 and 7 further illustrate the arrangement of the locking channels44A-D, and FIG. 6, in particular, illustrates the laterally-extendingchannel segment which extends around the inner periphery of the valvemember 40. Note also in FIG. 7 that the overtravel spring 85 is capturedin a compressed condition between the bottom side of the locking tabs51A-D and the shoulder 41 on the opposite end of the valve member 40.

The overall assembly of the shuttle assembly 30 is shown in FIG. 8. Eachof the elements, namely, the valve member 40, the shuttle member 50, theovertravel spring 85 and the thermal actuators 70A, 70B have a commoncentral axis and thus a symmetrical longitudinal orientation.

The incorporation of the shuttle assembly 30 into the mixing valve 20 isshown in FIG. 9. The plug 25 captures the shuttle assembly 30 and thespring 82 in the housing 21. The mixing valve is then ready to installin a water system by connecting suitable inlet and outlet piping to theinlets 22, 23 and the outlet 24, respectively.

Operation of the mixing valve 20 is illustrated in FIGS. 10-13. Themixing valve 20 is set to produce a mixed outflow of water within apredetermined temperature range, taking into account the nominaltemperature of the cold and hot water flowing into the valve 20.

FIG. 10 illustrates the valve member position when only cold water isbeing supplied to the valve 20. This occurs transiently as necessarywhen too much hot water flow has heated the thermal actuators to thepoint where the temperature of the outlet flow is outside of limits, andwhen a long period of time with little or no flow has heated the valve20 significantly.

If set correctly, the mixture of hot water and cold water through themixing valve 20 results in an outflow which is within the desiredtemperature range. Thus, in FIG. 11 both hot water and cold water flowpast the valve member 40. As shown, movement of the valve member 40simultaneously increases the flow of hot water when the flow of coldwater is being decreased, and vice versa. The movement of the valvemember 40 acts as a form of servo-feedback device to constantly senseand correct imbalances in the inflow temperature of the water.

FIG. 12 illustrates the condition when only hot water is being passedinto the mixing valve 20 in order to compensate for a temperature whichis below the lower temperature range. The valve member 40 is thus at thetop of its movement range.

FIG. 13 illustrates the situation when a temperature imbalance on thehot side has called for cold water, but the temperature imbalance issuch that the thermal actuators 70A, 70B has caused the valve member 40to bottom out on the plug 25 at the bottom of the mixing valve 20, butis still expanding. In this case, the overtravel spring 85 is compressedby the further downward force by the shuttle member 50, preventingdamage to the valve 20. Correction of the overtravel conditionimmediately returns the mixing valve 20 to normal operation.

A temperature-actuated mixing valve is described above. Various detailsof the invention may be changed without departing from its scope.Furthermore, the foregoing description of the preferred embodiment ofthe invention and the best mode for practicing the invention areprovided for the purpose of illustration only and not for the purpose oflimitation-the invention being defined by the claims.

We claim:
 1. A temperature-actuated mixing valve for controlling outlet temperature in a fluid flow system including a valve housing having first and second fluid supply inlets for introducing first and second respective supply fluids and a fluid outlet for dispensing a fluid at a predetermined outflow temperature, said mixing valve including a shuttle assembly positioned in said housing, said shuttle assembly comprising: (a) a valve member mounted for movement within said housing responsive to the temperature of the supply fluids to vary the mixture ratio of the first and second supply fluids as required to dispense fluid at the predetermined outflow temperature; (b) a shuttle member positioned within said valve member and moveable as a unit therewith within a predetermined range of motion responsive to supply fluid temperature variation, said shuttle member including an elongate grip pad for permitting the shuttle member to be manually removed from the valve housing without the need for tools; (c) a thermal actuator of the type which converts thermal energy into mechanical movement by movement of a piston, a first end of said thermal element engaging said movable shuttle member and an opposing second end engaging a stationary portion of said housing whereby movement of the piston of the thermal actuator produces corresponding movement of the valve member; and (d) an overtravel spring captured in a compressed condition between said valve member and said shuttle member for maintaining the shuttle member and the valve member in a stationary condition relative to each other within the predetermined range of motion of the valve member and for permitting movement of the shuttle member relative to the valve member sufficient to accommodate movement of the piston of the thermal actuator when the valve member has reached its limit of travel without accommodating the full extent of movement of the piston of the thermal actuator.
 2. A temperature-responsive mixing valve according to claim 1, wherein said valve member is generally cylindrical and includes sealing means for sealing the valve member against fluid flow between the valve member and adjacent cylindrical walls of the valve housing.
 3. A temperature-responsive mixing valve according to claim 1, wherein said shuttle member includes retaining means for retaining said thermal actuator within said shuffle member while permitting movement of the piston responsive to the temperature of the inlet fluids.
 4. A temperature-responsive mixing valve according to claim 3, wherein said retaining means comprises a plurality of elongate fingers axially aligned with the longitudinal axis of the thermal actuator, each of said fingers having a radially inwardly-extending detent for interfering with movement of the thermal actuator beyond a predetermined range of motion for movably-capturing the thermal actuator within the shuttle member.
 5. A temperature-actuated mixing valve according to claim 1, wherein said grip pad extends along the longitudinal axis of the shuttle member.
 6. A temperature-actuated mixing valve according to claim 1, wherein said valve member includes an annular shoulder defining a support for said overtravel spring, and further wherein the valve member includes locking means for receiving and locking the shuttle member within the valve member, said locking means cooperating with said overtravel spring for maintaining the shuttle member and the valve member in the stationary condition relative to each other.
 7. A temperature-actuated mixing valve according to claim 6, wherein said locking means comprises a plurality of locking channels formed within the area of the valve member accommodated by the overtravel spring, each of said locking channels having a first segment communicating with an inwardly-facing end of the valve member, a second segment communicating with the first segment and extending peripherally around inner wall of the valve member and a third segment spaced apart from said first segment, communicating with said second segment and terminating at a blind end within the inner walls of the valve member, said plurality of locking channels adapted to receive respective ones of a plurality of locking tabs carried by said shuttle member and lock the shuttle member in the valve member by compressing the overtravel spring and passing the plurality of locking tabs through the first and second segments and to the blind end of the third segment of the locking channels.
 8. A temperature-actuated mixing valve according to claim 1, wherein said shuttle member comprises an elongate stem having an annular bore for receiving said thermal actuator therein for movement therein, retaining means for retaining said thermal actuator in said bore and locking means for locking said stem in said valve member.
 9. A temperature-actuated mixing valve according to claim 1, and including an adjusting bolt positioned in said housing and engaging an end of the thermal actuator remote from said valve member for permitting longitudinal adjustment of said thermal actuator relative to the valve member.
 10. A temperature-actuated mixing valve according to claim 1, wherein said thermal actuator comprises a pair of thermal actuators for increasing the effective range of temperature-responsive motion.
 11. A temperature-actuated mixing valve according to claim 3, wherein said retaining means comprises a cage within which said thermal actuator is captured.
 12. A method of controlling outlet temperature in a fluid flow system including a valve housing having first and second fluid supply inlets for introducing first and second respective supply fluids and a fluid outlet for dispensing a fluid at a predetermined outflow temperature, said mixing valve including a shuttle assembly positioned in said housing, and comprising the steps of: (a) mounting a valve member for movement within said housing responsive to the temperature of the supply fluids to vary the mixture ratio of the first and second supply fluids as required to dispense fluid at the predetermined outflow temperature; (b) moving a shuttle member positioned within said valve member as a unit with said valve member within a predetermined range of motion responsive to supply fluid temperature variation, said shuttle member including an elongate grip pad for permitting the shuttle member to be manually removed from the valve housing without the need for tools; (c) providing a thermal actuator of the type which converts thermal energy into mechanical energy by movement of a piston wherein a first end of said thermal element engages the movable shuttle member and an opposing second end engages a stationary portion of said housing whereby movement of the piston of the thermal actuator produces corresponding movement of the valve member; (d) maintaining the shuttle member and the valve member in a stationary condition relative to each other within the predetermined range of motion of the valve member; and (e) permitting movement of the shuttle member relative to the valve member sufficient to accommodate movement of the piston of the thermal actuator when the valve member has reached its limit of travel without accommodating the full extent of movement of the piston of the thermal actuator.
 13. A method according to claim 12 and including the step of retaining the thermal actuator within a cage forming a part of the shuttle member for permitting movement of the thermal actuator within its range of motion while preventing the thermal actuator from falling out of the shuttle assembly.
 14. A method of controlling outlet temperature in a mixing valve of a fluid flow system including a valve housing having first and second fluid supply inlets for introducing first and second respective supply fluids and a fluid outlet for dispensing a fluid at a predetermined outflow temperature, said mixing valve including a shuttle assembly positioned in said housing and carrying a thermal actuator responsive to the temperature of fluid entering the mixing valve for controlling the ratio of the respective supply fluids to regulate the outflow temperature of the fluid, and comprising the steps of: (a) forming the shuttle assembly from a shuttle member and a valve member releasably-attached together, said shuttle member including an elongate grip pad for permitting said shuttle member to be manually removed from the valve housing without the need for tools; (b) retaining an overtravel spring between the shuttle member and said valve member; (c) moving the shuttle member and the valve member as a unit responsive to the thermal actuator when regulating the flow of fluid flowing into the mixing valve; and (d) moving the shuttle member relative to the valve member when compensating for overtravel of the thermal actuator. 